1. Field of the Invention
The present invention relates to the field of liquid crystal panel manufacturing, and in particular to a method for laminating glass panels and a vacuum lamination device using the method.
2. The Related Arts
Liquid crystal displays have a variety of advantages, such as thin device body, low power consumption, and being free of radiation, and are thus of wide applications, such as mobile phone, personal digital assistant (PDA), digital camera, computer monitor, and notebook computer screen.
Most of the liquid crystal displays that are currently available in the market are backlighting liquid crystal displays, which comprise an enclosure, a liquid crystal panel arranged in the enclosure, and a backlight module mounted in the enclosure. The structure of a conventional liquid crystal panel is composed of a color filter (CF) substrate, a thin-film transistor (TFT) array substrate, and a liquid crystal layer arranged between the two substrates and the operation principle is that a driving voltage is applied to the two glass substrates to control rotation direction of the liquid crystal molecules of the liquid crystal layer in order to refract out light emitting from the backlight module for generating images. Since the liquid crystal panel itself does not emit light, light must be provided from the backlight module in order to normally display images. Thus, the backlight module is one of the key components of a liquid crystal display. The backlight modules can be classified in two types, namely a side-edge backlight module and a direct backlight module, according to the position where light gets incident. The direct backlight module comprises a light source, such as a cold cathode fluorescent lamp (CCFL) or a light-emitting diode (LED), which is arranged at the backside of the liquid crystal panel to form a planar light source directly supplied to the liquid crystal panel. The side-edge backlight module comprises an LED light bar, serving as a backlight source, which is arranged at an edge of a backplane to be located rearward of one side of the liquid crystal panel. The LED light bar emits light that enters a light guide plate (LGP) through a light incident face at one side of the light guide plate and is projected out of a light emergence face of the light guide plate, after being reflected and diffused, to pass through an optic film assembly to form a planar light source for the liquid crystal panel.
Referring to FIG. 1, a schematic perspective view is given to show a conventional liquid crystal display, which comprises a backlight module 100, a mold frame 300 arranged on the backlight module 100, a liquid crystal display panel 500 arranged on the mold frame 300, and a bezel 700 mounted on the liquid crystal display panel 500. The backlight module 100 provides the liquid crystal display panel 500 with a planar light source of uniform illumination. The mold frame 300 carries and supports the liquid crystal display panel 500. The bezel 700 fixes the liquid crystal display panel 500 on the mold frame 300.
A general manufacturing process of liquid crystal display panel comprises a front stage of array process (including thin film, yellow light, etching, and film stripping), an intermediate stage of cell process (including bonding of TFT substrate and the CF substrate), and a rear stage of assembling process (including mounting of drive ICs and printed circuit board). The front stage of array process generally manufactures the TFT substrate in order to control the movement of liquid crystal molecules. The intermediate stage of cell process generally introduces liquid crystal between the TFT substrate and the CF substrate. The rear stage of assembling process generally mounts the drive ICs and combining the printed circuit board to effect driving the liquid crystal molecules to rotate for displaying images.
The conventional process of introducing liquid crystal between the TFT substrate and the CF substrate is generally a process referred to as one drop filling (ODF), of which the manufacturing process comprises: dropping a predetermined amount of liquid crystal on a TFT substrate on which a PI (Polyimide) film has been coated and laying a mold frame to show a designated pattern on a CF substrate on which a PI film has been coated, both being then forwarded into a vacuum lamination machine to be assembled together, followed by irradiation of UV (Ultraviolet) light to have the mold frame partially cured, and finally having them baked in an oven to have the mold frame to completely cured to compete the entire ODF process. In the process, the vacuum lamination and UV curing steps are of particularly importance for the product quality.
Referring to FIGS. 2-5, which illustrates a general process of vacuum lamination and UV curing that is conventionally used, specifically, the process comprises: firstly, laminating and assembling the TFT substrate 502 and the CF substrate 504 in a vacuum chamber in such a way that the precision of lamination is set to be of an error within ±5 um and may be within ±3 um for some high-end products, otherwise it might result in light leak of display, downgrading for poor quality product, or being directly disposed of. Then, a turn-over stage 503 is used to turn over the laminated TFT substrate 502 and the CF substrate 504 to prevent the UV light from incapable of irradiating seal resin 508 in the subsequent UV curing step due to the UV light being blocked by a black matrix (BM) 542 formed on the CF substrate 504. Finally, a UV lamp 505 and a UV mask 507 are used to irradiate the area of the seal resin 508 to cure the seal resin 508. The UV mask 507 shields the area of the liquid crystal 506 to avoid influence of the UV light on the property of the liquid crystal.
Such a conventional process has the following disadvantages:
(1) After the TFT substrate and the CF substrate have been laminated but before they are subjected to the irradiation of the UV light, since the seal resin has not yet been cured, turning over may result in a great deviation from the desired assembling precision due to the deformation of the substrates, so that the lamination precision may get larger than 5 um after the irradiation of the UV light and eventually, downgrading or disposal of the product ma result.
(2) Similarly, after the TFT substrate and the CF substrate have been laminated but before they are subjected to the irradiation of the UV light, since the seal resin has not yet been cured, if it would be of a long time (generally around 10 minutes) not subjecting to UV irradiation, molecules of the seal resin may get into the liquid crystal to cause contamination and affecting the performance of displaying; if the time is further extended, then the liquid crystal may penetrate through the seal resin to cause disposal of product, this generally occurring in abnormality of transporting device or malfunctioning of UV irradiating facility.
(3) Irradiation carried out with the UV irradiating facility is generally non-parallel light irradiation so that if size and location of an opening formed in a UV mask are not correct, then liquid crystal located around the seal resin may get exposed to irradiation of the UV light and reaction occurs. This makes it difficult to get a desired pre-tilt angle in a liquid crystal alignment step in the subsequent manufacturing process and leads to alignment abnormality of the product.